Three-component xerographic toner



March 5, 1963 c. J. CLAUS 3,089,318

THREE-COMPONENT XEROGRAPHIC TONER Filed March 1a, 1958 LIQUID HYDROPHILIC COLLOID HYDROPHOBIC RESIN INVENTOR.

Carl J. Claus ATTORNEY United States Patent 01 3,080,318 THREE-COMPQNENT XEROGRAPHIC TONER Carl J. Claus, Rochester, N.Y., assignor to Xerox Corporation, a corporation of New York Filed Mar. 13, 1958, Ser- No. 721,200 1 Claim. (Cl. 252-621) This invention relates in general to electrostatic recording and in particular to materials for xerography.

In the art of xerography, it is usual to form an electrostatic image on a suitable insulating or photoconductive insulating surface and to develop this image, or in other words make it visible, by presenting to the surface an electroscopic marking material. In the usual embodiments of xerography the electrostatic image is formed on a photoconductive insulating surface by charging the surface and exposing it to an image of light and shadow to be recorded whereupon the electric charge is dissipated in the light areas. Conventionally the image is then developed by dusting the image bearing surface with highly colored pigment materials such as, for example, pigmented thermoplastic resins. Because of the requirements of transfer of the powder and re-use of the photoconducting surface and for other reasons, xerographic development has been usually limited to dry materials. In these prior procedures, therefore, it has generally been necessary to employ subsequent fixing steps or operations in order to cause the image material to adhere permanently either to the original image bearing surface or to such other surface as shall be desired for a final image support member. Existing fixing operations have generally been limited to fusing the image material by means of heat or solvent vapor, although other methods such as lacquer spraying, overlaying and the like have occasionally been employed.

An object of the present invention is to provide new image materials for electrostatic recording wherein an electrostatic image may be developed and fixed.

Another object of the invention is to provide a new electroscopic image developing material for xerographic recording which image material is capable of being deposited in response to an electrostatic charge pattern and subsequently fixed on an image support surface by means of pressure.

An additional object of the invention is to provide a new xerographic developing material comprising an encapsulated marking material including a liquid droplet of a color composition within a shell having surface triboelectric properties suitable for electrostatic deposition.

Additional objects of the invention will in part be obvious and will in part become apparent from the following specification and drawing in which: The FIGURE is a diagrammatic view of a developer powder particle according to one form of the invention.

It has recently been found that suitable liquid materials can be formed into an extremely finely divided dry composition by separate encapsulation of appropriate liquid droplets within a hydrophilic shell. For example, in U.S. Patent 2,800,458, there is disclosed a manufactured preparation of oil-containing capsules of hardened gelatin. Such compositions have numerous uses in pressure recording arts. Unfortunately, it has been found that these compositions are essentially unsatisfactory for electrostatic recording because of their extreme variability in triboelectric properties depending on humidity in the atmosphere. It has now been found that image forming powders of proper triboelectric properties can be produced by encapsulating a liquid droplet of a suitable marking material within a hydrophilic coating such as gelatin or the like, and in turn encapsulating the hydrophilic material within a tough hydrophobic resin coating. In particular, cuter coatings of the polystyrene 2 family including polymerized styrene, polystyrene homologues and mixtures and copolymers thereof, and resins of the acrylic esters acrylic amide and methacrylic esters and amides and mixtures of copolymers thereof, as well as mixtures of styrene and acrylic resins may be produced on hydrophilic capsules by immersion in polymer solutions followed by drying or evaporation of the solvent to produce developer materials for xerography.

The new developer powder composition includes essentially three separate phases or components such as, for example a liquid droplet 10 encased in a hydrophilic coating 11, in turn within a hydrophobic resin coating 12. The. liquid composition comprises essentially an oil base dye, ink, or the like, containing a highly colored material suchas a pigment or dye generally capable of permanently coloring an image support sheet such as, for example, a sheet of paper or the like. Suitable oil bases include oils and other non-polar fluids generally not miscible with water but such as for example waxes, mineral oils, animal oils and the like, as well as vegetable oils. such as olive oil, castor oil, and the like. Desirably, an oil composition may include a. solution of a resin material in a suitable solvent such as for example a hydrocarbon solvent together with a dye or a pigment material including for example, finely divided carbon. Inparticular, it is specifically a part of this invention that the oil composition may be chemically active with or incompatible with the hydrophobic resin coating 12.

The oil composition is contained within a hydrophilic colloid material such as, for example, gelatin casing or the like and may be formed into an encapsulated powder with materials and methods disclosed in Green et al. U.S. Patent 2,800,457. Suitable encapsulating material. includes gelatin, hydrophilic cellulose materials such as hydrophilic cellulose esters and ethers, gums and the like.

Suitable capsules such as, for example, capsules as disclosed in the Green et al. patent may be coated with a resin to form a xerographic developer composition. As a preferred procedure, the gelatin capsule material is dipped or immersed into a solution of a mixture of polystyrene and polystyrene homologues dissolved in toluene, xylene, or a similar non-aqueous organic solvent. The mixture is suitably agitated and dried by spray drying or the like to produce capsules substantially uniformly coated with the polystyrene type resin. According to a presently preferred procedure a polystyrene type material believed to consist of a polymerized mixture of styrene and styrene homologues and available under the name Piccolastic D-l25 is employed. This resin is dissolved in xylene, and the capsules are immersed in the solution. Excess liquid is filtered ofl. and the coated capsules air dried with occasional mixing. Alternatively the capsules may be dried according to conventional spray drying procedures.

In the preferred procedure for producing a xerographic developer the polystyrene coated capsule powder is mixed with a granular bead-like carrier material such as disclosed in Walkup patent U.S. 2,816,551, generally in the amount of 1% of the powder composition and 99% of the carrier composition. The mixed developer material is useful in xerographic image development as, for example, by cascading the mixture across the surface of the electrostatic image bearing xerographic plate or across the surface of an electrostatic image bearing insulating surface.

Alternatively, the powder material may be employed for image development by blowing it into an air cloud and directing the air cloud to the image surface, by mixing the powder material with a ferromagnetic material and magnetically conveying the mixture into brushing contact with the image surface, or by dusting the powder material into a brush such as, for example, a fur brush and brushing the image surface. Other image development methods may include dispersing the powder in an inert liquid and applying a liquid suspension by dipping or immersing or by pouring the liquid suspension across the image surface or the like. 7

Upon image development in any of these methods it has been found that a visible powder image is formed on the image bearing surface. The image may be permanently afiixed to the surface by means of pressure rollers or the like, or may be transferred to an adjacent surface and subsequently afiixed to such an adjacent surface. Thus, for example, a Xerographic image may be formed on a selenium coated metal plate or drum by applying an electrostatic charge to the selenium surface. The image may be developed by the methods of the invention and transferred to a piece of paper placed in contact with the image bearing selenium plate or drum by means of corona discharge or the like and the image permanently aflixed to the paper by means of pressure rollers. Likewise, an electric image formed on a paper backed photoconductor such as zinc oxide in an insulating silicone, polystyrene, acrylic resin or the like, may be developed and fixed in situ.

The present invention permits the use for Xerography of a wide variety of color marking materials including dyes, inks, or the like, Without regard to the triboelectric properties of such marking materials. There may be employed, for example, carbon black materials prepared and coated according to this invention to have suitable triboelectric properties as well as dyes, pigments, or the like, of various colors dispersed or dissolved in oil base. The xerographic developer compositions prepared with such marking materials are independent of the triboelectric characteristics of the marking material itself or of the encapsulating materials in which the marking materials are encased. It has been found that desired triboelectricity and humidity resistance can be imparted to the composition by polymerized styrene and polymerized acrylic resins and that such resins may be employed Without regard to the nature of the marking material or to oil base.

What is claimed is:

A pressure fixing xerographic toner composition consisting of particles triboelectrically adapted independently of ambient humidity and in a size range for use in conjunction with a Xerographic carrier to form a tonercarrier system for developing Xerographic images, said particles consisting of an inner core of oil base marking liquid encapsulated in a rupturable hardened hydrophiiic colloid shell, and an outer rupturable shell of hydrophobic resin coated on said colloid shell, said hydrophobic resin being triboelectrically adapted for use With a xerographic carrier and selected from the group consisting of polystyrene resins and polyacryiic resins.

References Cited in the tile of this patent UNITED STATES PATENTS 2,512,192 Yen et a1 June 20, 1950 2,712,507 Green July 5, 1955 2,730,456 Green et al. Ian. 10, 1956 2,784,109 Walkup Mar. 5, 1957 2,788,288 Rheinfrank et al Apr. 9, 1957 2,800,458 Green July 23, 1957 2,877,133 Mayer Mar. 10, 1959 2,953,470 Green et al Sept. 20, 1960 FOREIGN PATENTS 20,726 Great Britain of 1910 734,909 Great Britain Aug. 10, 1955 1,112,180 France Nov. 9, 1955 760,403 Great Britain "Oct. 31, 1956 

